Characterizing the acquisition of mouse XEN cell identity during the second cell fate decision in the early blastocyst

During the second cell fate decision occurring in the early blastocyst, the ICM differentiates into two cell compartments; the epiblast which will give rise to the embryo proper, and the extra embryonic lineage termed the Primitive Endoderm (PrE). These cells create a barrier between the pluripotent cells and the cavity of the blastocyst and will contribute to the yolk sac.

In recent years, following the work of Yamanaka and others, the reprogramming process of somatic cells is used as a research tool to investigate cell fate decision. The advantage of this approach is the ability to identify the core circuitry genes that are responsible for cell fate identity. Furthermore, it allows to follow transcriptomic and epigenetic changes that occur in the process.

Pluripotent cells have been extensively studied both in terms of the molecular process and the quality of cells obtained by reprogramming, yet the Primitive Endoderm cells, also called XEN (extra embryonic endoderm) cells, are less investigated.

we successfully derived XEN cell lines, which represent the PrE cells in vitro, from different sources. iXEN (induced extra embryonic endoderm) cells by reprogramming mouse embryonic fibroblast (MEF) using various combinations of factors and conditions, direct conversion from ESC, and an endogenous cell line from the blastocyst as a control. The goal of this study is to determine the crucial factors that are responsible for the XEN cell identity.